The present invention relates to a bulk material separator having an at least essentially coaxial arrangement of an essentially rotationally symmetric, vertically oriented separator jacket having an output port for air and light bulk material fractions in the upper section and a narrowed section, followed by and expanding guide funnel. The bulk material separator also includes a bulk material feed tube connected to the top of separator jacket and directed downwardly and terminating in the region of the narrowed section, a displacement body that is coaxial with the bulk material feed tube and disposed at least in the region of the guide funnel and has an upwardly pointing conical tip, and a container surrounding at least the guide funnel and the displacement body and provided with a separator air inlet port.
A separator of this type is known from DE 44 16 757 A1. This separator is designed to provide a constant air velocity across the cross-section in the annular space between the bulk material feed tube and the displacement body projecting far into the feed tube. For this purpose, the inner wall of the cylindrical bulk material feed tube and the jacket of the cylindrical displacement body are provided with a surface structure that increases the roughness. In the elongated annular space of the known separator, the bulk material particles relatively frequently impact the inner wall of the bulk material feed tube and/or the jacket of the displacement body and slow down with each impact. This can produce so-called shot grain. These are bulk material particles, which because of their low velocity are entrained in the separator air, although they are not part of the constituents of the bulk material to be separated. Contact between the bulk material particles and the walls also promotes the generation of dust and thread-like abrasion. Consumption of separator air is also relatively high, since a portion of the separator air flows upwardly into the separator jacket without prior intensive contact with the bulk material particles.